Bearing assemblies, bearing apparatuses, and methods of use

ABSTRACT

Embodiments of the invention relate to bearing assemblies, bearing apparatuses, and methods of assembling and operating such bearing assemblies and apparatuses. For instance, first bearing assembly and/or the second bearing assembly may include one or more tapered sections, which may facilitate entry of the first bearing assembly into the second bearing assembly.

BACKGROUND

Bearing assemblies and apparatuses may commonly be used to facilitaterotation of a machine element or component relative to another machineelement or component. For instance, a radial bearing apparatus mayfacilitate rotation of a shaft relative to a housing. In particular, theradial bearing apparatus may allow the shaft to rotate relative to thehousing while limiting or preventing lateral movement of the shaft.Furthermore, in some instances the shaft also may be restricted fromaxial movement by one or more thrust-bearing assemblies. In any case,the bearing assemblies and/or bearing apparatuses may facilitaterotation of the shaft, while preventing or limiting non-rotationalmovement thereof relative to the housing.

A typical bearing apparatus includes a stator that does not rotate and arotor that is attached to the shaft and rotates with the shaft. Theoperational lifetime of the bearing apparatuses often determines theuseful life of the machine.

Therefore, manufacturers and users of machines that include rotatingelements or components continue to seek improved bearing apparatuses toextend the useful life of such bearing apparatuses.

SUMMARY

Embodiments of the invention relate to bearing assemblies, bearingapparatuses, agitator systems including such bearing assemblies andapparatuses, and methods of assembling and operating such bearingassemblies and apparatuses. In an embodiment, a bearing assemblyincludes a support structure having a bearing section and a taperedsection connected to the bearing section. The tapered section includes asubstantially conically shaped outer surface. A plurality of firstsuperhard bearing elements are secured to the bearing section of thesupport structure, with the plurality of first superhard bearingelements being distributed about an axis to form a radial bearingsurface. Each of the plurality of first superhard bearing elementsincludes a superhard material having a first superhard bearing surface.A plurality of second bearing elements are secured to one or more of thebearing section or the tapered section of the support structure.

In an embodiment, a bearing apparatus is disclosed. The bearingapparatus includes a first bearing assembly including a supportstructure, a plurality of first superhard bearing elements secured tothe support structure and each having a first superhard bearing surface,and a plurality of second superhard bearing elements secured to thesupport structure. Each of the plurality of second superhard bearingelements includes a beveled surface. The plurality of first superhardbearing elements and the plurality of second superhard bearing elementsat least partially define an opening in the first bearing assembly. Theplurality of second superhard bearing elements at least partially form afirst tapered section of the first bearing assembly. The bearingapparatus further includes a second bearing assembly insertable into thefirst bearing assembly. The second bearing assembly includes a pluralityof third superhard bearing elements each having a third superhardbearing surface sized and configured to rotatably engage the firstsuperhard bearing surfaces.

In an embodiment, an agitator system is disclosed. The agitator systemincludes a container sized and configured to contain a medium, a firstbearing assembly secured to a bottom of the container, a shaft includingone or more blades attached thereto, and a second bearing assemblysecured to the shaft and insertable into the first bearing assembly. Thefirst bearing assembly includes a plurality of first superhard bearingelements each having a first superhard bearing surface, and the firstbearing surfaces defining an opening in the first bearing assembly. Thesecond bearing assembly includes a support structure having a taperedsection, and a plurality of second superhard bearing elements secured tothe support structure and each having a second superhard bearing surfaceconfigured to rotatably engage the first superhard bearing surfaces. Thetapered section is sized and configured to substantially align agenerally center axis of the second bearing assembly with a generallycenter of the first bearing assembly.

Features from any of the disclosed embodiments may be used incombination with one another, without limitation. In addition, otherfeatures and advantages of the present disclosure will become apparentto those of ordinary skill in the art through consideration of thefollowing detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate several embodiments of the invention, whereinidentical reference numerals refer to identical or similar elements orfeatures in different views or embodiments shown in the drawings.

FIG. 1A is an isometric view of a first bearing assembly connected to ashaft according to an embodiment of the invention;

FIG. 1B is a cross-sectional view of the first bearing assembly of FIG.1A;

FIG. 1C is a cross-sectional view of first bearing assembly according toanother embodiment of the invention;

FIG. 1D is an enlarged partial cross-sectional view of a bearing elementattached to a support structure of a first bearing assembly according toan embodiment of the invention;

FIG. 1E is an enlarged partial cross-sectional view of a bearing elementattached to a support structure of a first bearing assembly according toanother embodiment of the invention;

FIG. 2 is a cross-sectional view of first bearing assembly according toan embodiment of the invention;

FIG. 3 is a cross-sectional view of first bearing assembly according toanother embodiment of the invention;

FIG. 4 is a cross-sectional view of the first bearing assembly accordingto yet another embodiment of the invention;

FIG. 5 is a cross-sectional view of first bearing assembly according tostill another embodiment of the invention;

FIG. 6 is a cross-sectional view of a second bearing assembly accordingto an embodiment of the invention;

FIG. 7A is a cross-sectional view of misaligned first and second bearingassemblies during assembly of a bearing apparatus according to anembodiment of the invention;

FIG. 7B is a cross-sectional view of substantially aligned first andsecond bearing assemblies during assembly of a bearing apparatusaccording to an embodiment of the invention;

FIG. 8 is a cross-sectional view of a bearing apparatus according toanother embodiment of the invention;

FIG. 9 is a cross-sectional view of a bearing apparatus according to yetanother embodiment of the invention; and

FIG. 10 is a cross-sectional view of an agitator system according to anembodiment of the invention.

DETAILED DESCRIPTION

Embodiments of the invention relate to bearing assemblies, bearingapparatuses, agitator systems including such bearing assemblies andapparatuses, and methods of assembling and operating such bearingassemblies and apparatuses. In particular, an embodiment may include afirst radial bearing assembly insertable into a second radial bearingassembly. For instance, the first bearing assembly may be a rotor andthe second bearing assembly may be a stator, or vice versa. Furthermore,the first bearing assembly and/or the second bearing assembly mayinclude one or more tapered sections (e.g., lead-in sections), which mayfacilitate entry of the first bearing assembly into the second bearingassembly.

An embodiment may include a tapered section on the first and/or secondbearing assemblies. For instance, the first and/or second bearingassemblies may include a beveled or tapered section, which mayfacilitate alignment or centering of the first and second bearingassemblies. Particularly, one or more tapered section may guide thecorresponding first and/or second bearing assemblies to a concentricposition relative to each other. Accordingly, in some embodiments, oneor more tapered section may reduce or eliminate damaging the firstand/or second assemblies during assembly of the bearing apparatuscomprising thereof.

Also, in an embodiment, the first and/or second bearing assemblies mayinclude superhard bearing elements. As used herein, a “superhard bearingelement” is a bearing element including a bearing surface that is madefrom a material exhibiting a hardness that is at least as hard astungsten carbide. In any of the embodiments disclosed herein, thesuperhard bearing elements may include one or more superhard materials,such as polycrystalline diamond, polycrystalline cubic boron nitride,silicon carbide, tungsten carbide, or any combination of the foregoingsuperhard materials.

In some embodiments, any of the respective support structures also mayinclude a tapered section that may at least partially form the lead-insection of the first and/or second bearing assemblies. Moreover, in anembodiment, the superhard bearing elements may protrude outward fromcorresponding support structures of the first and/or second bearingassemblies. Accordingly, in some embodiments, the superhard bearingelements may include and/or at least partially form the lead-in sectionof the first and/or section bearing assemblies. For instance, a taper orbevel may extend from a bearing surface of any one of the superhardbearing elements toward the support structure (e.g., toward a taperedsection or bearing section of the support structure). For example, thetapered section of the support structure may include a bevel of thesuperhard bearing elements.

FIG. 1A illustrates a first bearing assembly 100 according to anembodiment. The first bearing assembly 100 includes a support structure110 and a plurality of superhard bearing elements 120 (e.g., superhardbearing elements 120 a-120 c) secured to and/or within the supportstructure 110. Moreover, the first bearing assembly 100 may attach orconnect to a shaft 20. In particular, rotation of the shaft 20 mayproduce a corresponding rotation of the first bearing assembly 100(e.g., the shaft 20 and the first bearing assembly 100 may rotateapproximately concentrically). It should be appreciated that the terms“first” and “second” bearing assembly are used for descriptive purposesonly and are not intended to specifically identify either bearingassembly as a rotor, stator, or a particular type of a bearing assembly.Hence, the terms “first” and “second” may be used interchangeably.

As noted above, in some instances, at least some of the superhardbearing elements 120 may at least partially form a tapered section ofthe first bearing assembly 100. As such, in some instances, one or moreof the superhard bearing elements 120 may have different shapes and/orconfigurations than other superhard bearing elements 120. For example,superhard bearing elements 120 a, 120 b may have an approximatelyrectangular shape, while superhard bearing elements 120 c may have anapproximately rectangular shape with a bevel on one side thereof.

In any event, however, each of the superhard bearing elements 120 mayinclude a bearing surface that may engage one or more bearing surfacesof the second bearing assembly. For instance, the superhard bearingelements 120 c may include bearing surfaces 121 c. Similarly, thesuperhard bearing elements 120 a, 120 b may include respective bearingsurfaces 121 a, 121 b. In the illustrated embodiment, the first bearingassembly 100 is a radial bearing assembly. Accordingly, at least one,some, or each of the superhard bearing elements 120 may have a convexbearing surface (e.g., curved to form an exterior surface of a portionof an imaginary cylinder), such as the bearing surfaces 121 a, 121 b,121 c.

As described below in further detail, the bearing surfaces of theopposing, second bearing assembly may be configured to engage thebearing surfaces 121 a, 121 b, 121 c. For example, at least one, some,or each of the bearing surfaces of the second bearing assembly may havea concave configuration (e.g., curved to form an interior surface of aportion of an imaginary cylinder). In any event, the superhard bearingelements 120 may rotationally engage the superhard bearing elements ofthe second bearing assembly in a manner that facilitates rotation of thefirst bearing assembly 100 (e.g., about axis 10) relative to and/orwithin the second bearing assembly, while limiting or preventing lateralmovement thereof.

The first bearing assembly 100 may include the superhard bearingelements 120 arranged in any suitable manner on and/or about the supportstructure 110. For example, the superhard bearing elements 120 may formmultiple columns. One embodiment may include four columns of thesuperhard bearing elements 120 positioned circumferentially about theaxis 10. Embodiments also may include more or fewer than four columns(e.g., each column spaced at 90 degrees apart) of the superhard bearingelements 120. Furthermore, spacing between the columns may vary from oneembodiment to the next, and may depend on the number of columns, widthof the superhard bearing elements 120, as well as relative position ofthe superhard bearing elements 120 in the adjacent columns.

In addition, the columns may be axially aligned with one another (i.e.,the superhard bearing elements 120 in one column may be aligned with thesuperhard bearing elements 120 and the adjacent column). Alternatively,the columns may be offset (e.g., circumferentially and/or radiallyoffset) from one another, such that the superhard bearing elements 120in one column are offset from the superhard bearing elements 120 in anadjacent column. Also, the columns of the superhard bearing elements 120may be approximately oriented axially along the length of the supportstructure 110 or at selected distances along the axis 10. Accordingly,rotation of the support structure 110 about a center axis thereof and/orabout the axis 10 may produce rotation of the columns of the superhardbearing elements 120 about the axis 10.

In additional or alternative embodiments, the column of the superhardbearing elements 120 may be oriented and/or positioned in any desiredconfiguration relative to the length of the support structure 110 (e.g.,the column of the superhard bearing elements 120 may approximately forma spiral or helix about an outer surface 130 of the support structure110). Also, the first bearing assembly 100 may include any number of thesuperhard bearing elements 120 positioned along the length thereof. Forinstance, the superhard bearing elements 120 may form rows that spanabout the support structure 110 (e.g., about the circumference of thesupport structure 110). In any event, the bearing surfaces 121 a, 121 b,121 c may rotate about the axis 10 in a manner that the path thereofapproximates a cylindrical surface.

As the first bearing assembly 100 rotates about the axis 10, one side ofthe superhard bearing elements 120 will be a front or a leading side,while another side may be a trailing side. For example, the superhardbearing elements 120 a may include a leading side 122 c and a trailingside 123 c. In at least one embodiment, one, some, or all of thesuperhard bearing elements 120 may include a chamfer between the bearingsurfaces and the leading sides (e.g., on the superhard bearing elements120 c, the chamfer may extend between the bearing surface 121 c and theleading side 122 c). Alternatively, the interface between the leadingside and the bearing surface of one, some, or all of the superhardbearing elements 120 may be a sharp edge.

Also, as noted above, the superhard bearing elements 120 also may have abeveled surface, which may facilitate assembly of the bearing apparatusdescribed below. In an embodiment, the superhard bearing elements 120 cmay include a beveled surfaces 124 c. In some embodiments, the beveledsurfaces 124 c may be approximately perpendicular relative to theleading side 122 c. Alternatively, however, the beveled surface 124 cmay form any suitable angle with the leading side 122 c. The beveledsurfaces 124 c also may have a partially substantially cylindrical orconvex shape, similar to the shape of the bearing surface 121 c. Forinstance, the beveled surfaces 124 c may be shaped as a portion of asubstantially cylindrical cone. Additionally, the beveled surfaces 124 cmay form an obtuse angle relative to the 121 c. One, some, or all of thebeveled surfaces 124 c of the superhard bearing elements 120 c may forma portion of or may lie on an imaginary conical surface.

In the illustrated embodiment, the superhard bearing elements 120 havechamfered corners or edges on leading edges or along leading sides 122 cof the bearing surfaces. In some operating conditions, such sharpcorners or edges may result in premature chipping or cracking of thesuperhard bearing elements 120 and of the bearing surfaces inparticular. It should be appreciated, however, that embodiments also mayinclude the superhard bearing elements 120 may have chamfers, radii, orother features that may reduce or eliminate chipping of the superhardbearing elements 120. For example, each, some, or all of the superhardbearing elements 120 may have a chamfer or a radius that span about aperimeter of the respective bearing surfaces.

In some embodiments, the beveled surface 124 c may be approximatelyperpendicular relative to the leading side 122 c. Alternatively,however, the beveled surface 124 c may form any suitable angle with theleading side 122 c. The beveled surface 124 c also may have a partiallysubstantially cylindrical or convex shape, similar to the shape of thebearing surface 121 c. For instance, the beveled surface 124 c may beshaped as a portion of a substantially cylindrical cone. Additionally,the beveled surface 124 c may form an obtuse angle relative to the 121c.

Furthermore, the support structure 110 may include a bearing section 111and a tapered section 112, which may be located at a distal end thereof.The tapered section 112 may have a substantially conical shape. Inparticular, the configuration of the tapered section 112 may vary fromone embodiment to the next and may depend on the size of the supportstructure 110, length of the support structure 110, as well as otherparameters or factors. In one embodiment, the tapered section 112 mayhave an included angle θ of approximately 30° to approximately 60°.

In an embodiment, at a proximal end thereof, the bearing section 111 maymount or attach to a shaft 20. At the distal end, the bearing section111 may attach to or may be integrated with the tapered section 112. Forexample, the distal end of the first bearing assembly 100 may beinserted into the second bearing assembly. As such, the tapered section112 as well as the beveled surface 124 c of the superhard bearingelements 120 c may facilitate entry of the first bearing assembly 100into the second bearing assembly and may assist in substantiallyconcentric alignment thereof.

More specifically, as noted above, the superhard bearing elements 120may be secured to the bearing section 111 of the support structure 110.In some embodiments, the tapered section 112 may be free of thesuperhard bearing elements 120. Alternatively, as described in moredetail below, the tapered section 112 may include at least one or aplurality of superhard bearing elements. In any event, at least aportion of in the superhard bearing elements 120 and/or the taperedsection 112 may facilitate assembly of the bearing apparatus (i.e.,entry of the first bearing assembly 100 into the second bearingassembly).

In some embodiments, as illustrated in FIG. 1B, the superhard bearingelements 120 and any superhard bearing element disclosed herein may haverespective superhard tables 125 a-125 c and substrates 126 a-126 c. Forexample, the superhard tables 125 a-125 c may comprise polycrystallinediamond and the substrate substrates 126 a-126 c may comprisecobalt-cemented tungsten carbide. Other carbide materials may be usedwith tungsten carbide or as an alternative, such as chromium carbide,tantalum carbide, vanadium carbide, titanium carbide, or combinationsthereof cemented with iron, nickel, cobalt, or alloys thereof.Furthermore, in any of the embodiments disclosed herein, thepolycrystalline diamond table may be leached to at least partiallyremove or substantially completely remove a metal-solvent catalyst(e.g., cobalt, iron, nickel, or alloys thereof) that was used toinitially sinter precursor diamond particles to form the polycrystallinediamond. In another embodiment, an infiltrant used to re-infiltrate apreformed leached polycrystalline diamond table may be leached orotherwise removed to a selected depth from a bearing surface. Moreover,in any of the embodiments disclosed herein, the polycrystalline diamondmay be un-leached and include a metal-solvent catalyst (e.g., cobalt,iron, nickel, or alloys thereof) that was used to initially sinter theprecursor diamond particles that form the polycrystalline diamond and/oran infiltrant used to re-infiltrate a preformed leached polycrystallinediamond table. Examples of methods for fabricating the superhard bearingelements and superhard materials and/or structures from which thesuperhard bearing elements disclosed herein may be made are disclosed inU.S. Pat. Nos. 7,866,418; 7,998,573; 8,034,136; and 8,236,074; thedisclosure of each of the foregoing patents is incorporated herein, inits entirety, by this reference.

The diamond particles that may be used to fabricate any of the superhardtables 125 a-125 c in a high-pressure/high-temperature process (“HPHT)”may exhibit a larger size and at least one relatively smaller size. Asused herein, the phrases “relatively larger” and “relatively smaller”refer to particle sizes (by any suitable method) that differ by at leasta factor of two (e.g., 30 μm and 15 μm). According to variousembodiments, the diamond particles may include a portion exhibiting arelatively larger size (e.g., 70 μm, 60 μm, 50 μm, 40 μm, 30 μm, 20 μm,15 μm, 12 μm, 10 μm, 8 μm) and another portion exhibiting at least onerelatively smaller size (e.g., 15 μm, 12 μm, 10 μm , 8 μm, 6 μm, 5 μm, 4μm, 3 μm, 2 μm, 1 μm, 0.5 μm, less than 0.5 μm, 0.1 μm, less than 0.1μm). In an embodiment, the diamond particles may include a portionexhibiting a relatively larger size between about 10 μm and about 40 μmand another portion exhibiting a relatively smaller size between about 1μm and 4 μm. In another embodiment, the diamond particles may include aportion exhibiting the relatively larger size between about 15 μm andabout 50 μm and another portion exhibiting the relatively smaller sizebetween about 5 μm and about 15 μm. In another embodiment, therelatively larger size diamond particles may have a ratio to therelatively smaller size diamond particles of at least 1.5. In someembodiments, the diamond particles may comprise three or more differentsizes (e.g., one relatively larger size and two or more relativelysmaller sizes), without limitation. The resulting polycrystallinediamond formed from HPHT sintering the aforementioned diamond particlesmay also exhibit the same or similar diamond grain size distributionsand/or sizes as the aforementioned diamond particle distributions andparticle sizes. Additionally, in any of the embodiments disclosedherein, the superhard bearing elements may be free-standing (e.g.,substrateless) and optionally may be at least partially or fully leachedto remove a metal-solvent catalyst initially used to sinter thepolycrystalline diamond body.

As described above, in some embodiments, the superhard bearing elements120 may be secured to or integrated with the support structure 110. Forexample, the support structure 110 may include recesses 113 (FIG. 1B),and the superhard bearing elements 120 may be secured within therecesses 113. In an embodiment, the substrates of the superhard bearingelements 120 may be secured within the recesses 113. Alternatively, asmentioned above, some or all of the superhard bearing elements 120 maybe substrateless. As such, corresponding superhard tables of thesuperhard bearing elements 120 may be secured within the recesses 113.Furthermore, a portion of one, some, or all of the substrates mayprotrude out of the support structure 110. Alternatively, one, some, orall of the substrates may be located completely inside the supportstructure 110, such that only the respective superhard tables 125 a-125c protrude out of the support structure 110. Also, in some embodiments,the bearing surfaces of the superhard bearing elements 120 (as formed ordefined by the superhard table 125 a-125 c) may be flush with thesupport structure 110.

The superhard bearing elements 120 may be secured to the supportstructure 110 in any number of suitable ways that may vary from oneembodiment to the next. For instance, the superhard bearing elements 120may be at least partially secured within respective recesses 113 in thesupport structure 110 by brazing, press-fitting, threadedly attaching,fastening with a fastener, combinations of the foregoing, or anothersuitable technique. In any case, the superhard bearing elements 120 maybe removably or non-removably secured to the support structure 110, suchas to remain attached to the support structure 110 during the operationof the first bearing assembly 100.

As mentioned above, the first bearing assembly 100 may be attached to ashaft. For example, the first bearing assembly 100 may include anopening 150 that may accept a corresponding portion of the shaft and mayalign the first bearing assembly 100 relative to the shaft (e.g., mayalign the shaft concentrically with the first bearing assembly 100). Insome embodiments, the opening 150 may include a female thread, while theshaft may include a corresponding male thread, which may engage and matewith the female thread, thereby securing together the first bearingassembly 100 and the shaft. Alternatively, the shaft may include femalethread that may engage and couple with a male-threaded protrusionincluded in the first bearing assembly (e.g., as shown in FIG. 4).

Moreover, in some embodiments, the first bearing assembly may include ahole that may accept or slip over a shaft. For instance, the shaft maybe press-fit in the hole. One embodiment includes a first bearingassembly 100 a that includes a through hole 150 a, as shown in FIG. 1C.Except as otherwise described herein, the first bearing assembly 100 aand its respective materials, elements, or components may be similar toor the same as the first bearing assembly 100 (FIGS. 1A-1B) and theirrespective materials, elements, and components. In some embodiments, theshaft may be cooled and/or at least a portion of the first bearingassembly 100 a may be heated to facilitate press-fit of the shaft in thehole 150 a.

Furthermore, it should be also appreciated, however, that the hole mayhave any suitable depth in the first bearing assembly. Additionally, thethrough hole 150 a may facilitate fastening the first bearing assembly100 a to the shaft. For example, the shaft may include a female threadon end thereof, which may be accessible through the distal end of thethrough hole 150 a. Hence, the first bearing assembly 100 a may befastened to the shaft with a washer that may be hold the first bearingassembly 100 a on the shaft with an aid of a screw threaded into thefemale thread of the shaft.

As mentioned above, the substrate may be at least partially or entirelycontained within the support structure 110 (e.g., a portion of thesubstrate may protrude out of the support structure 110). FIG. 1Dillustrates one embodiment that includes the superhard bearing element120 c having the substrate 126 c positioned radially within the recess113 in the bearing section 111 of the support structure 110. In otherwords, only the superhard table 125 c may protrude above the radialouter surface 130 of the bearing section 111 of the support structure110, while the substrate 126 c may be positioned radially within therecesses 113. In addition, the beveled surface 124 c may extend betweenthe bearing surface 121 c and a peripheral surface or edge of thesuperhard bearing element 120 c. As such, a lower edge of the beveledsurface 124 c may be spaced away from the outer surface 130, such thatthere is a gap between the tapered section 112 and the beveled surface124 c.

In an embodiment, however, the beveled surface 124 c may extend betweenthe bearing surface 121 c and the outer surface 130. For example, thesuperhard bearing elements 120 c may be positioned on the bearingsection 111 such that the beveled surface 124 c forms a substantiallyuninterrupted portion of the tapered section 112.

In additional or alternative embodiments, each, some, or all of thesuperhard bearing elements may include the substrate that protrudesradially beyond the support structure (i.e., protrudes beyond the outersurface of the support structure). FIG. 1E illustrates an embodimentthat include a superhard bearing element 120 c′ secured within therecess 113′ of the support structure 110′. Except as otherwise describedherein, the superhard bearing element 120 c′ and the support structure110′ and their respective materials, elements, or components may besimilar to or the same as the superhard bearing element 120 c and/or thesupport structure 110 (FIG. 1D) and their respective materials,elements, and components. Generally, the recess 113′ may have anysuitable depth within the support structure 110′, which may vary fromone embodiment to the next. In some embodiments, the superhard bearingelement 120 c′ may include the substrate 126 c′ that protrudes out ofthe recess 113′ and above the outer surface 130′ of the supportstructure 110′.

Furthermore, in some instances, superhard bearing element 120 c′ mayinclude beveled surface 124 c′ that may pass through a superhard table125 c′ as well as through the substrate 126 c′. In other words, thesuperhard table 125 c′ as well as substrate 126 c′ may together the formthe beveled surface 124 c′. In some embodiments, the beveled surface 124c′ may be included in tapered section 112′ of the support structure110′. In one embodiment, there may be a gap between the beveled surface124 c′ and the tapered section 112′. Alternatively, however, the taperedsection 112′ may be substantially continuous and may have not gapbetween the beveled surface 124 c′ and a distal end of the supportstructure 110′.

In additional or alternative embodiments, the tapered support region ofthe support structure may extend from a cylindrical section disposedbetween the tapered section of the superhard elements by and the taperedsupport region. For example, FIG. 2 illustrates a first bearing assembly100 b that has a support structure 110 b, which includes a taperedsection 112 b. Except as otherwise described herein, the first bearingassembly 100 b and its respective materials, elements, or components maybe similar to or the same as any of the first bearing assemblies 100,100 a (FIGS. 1A-1C) and their respective materials, elements, andcomponents.

In some embodiments, the tapered section 112 b of the first bearingassembly 100 b may transition to an approximately cylindrical section114 b. In at least one embodiment, the cylindrical section 114 b mayhave a larger diameter than at least another portion of the supportstructure 110 b. In any event, the cylindrical section 114 b may belocated between the tapered section 112 b″ and superhard bearingelements 120 b″. As noted above, one, some, or all of the superhardbearing elements 120 b″ may include a beveled surface 124 b″. Forinstance, the beveled surface 124 b″ may extend from a bearing surface121 b″ toward and/or to the cylindrical section 114 b.

In one or more embodiments, the cylindrical section 114 b may have asmaller diameter than the diameter formed or defined by the bearingsurfaces 121 b″ and/or by other bearing surfaces of the bearing elementsmounted on the support structure 110 b. In other words, the outersurface of the cylindrical section 114 b may be spaced apart frombearing surfaces of an opposing (e.g., second) bearing assembly.Alternatively, however, diameter of the cylindrical section 114 b may beapproximately the same or similar to the diameter formed by the bearingsurfaces 121 b″.

Moreover, in some examples, the first bearing assembly 100 b may includenotches formed by and between the beveled surfaces 124 b″ and a shoulderof the cylindrical section 114 b. Embodiments also may include thebearing elements 120 b″ abutting the cylindrical section 114 b in amanner that minimizes or eliminate any notches and/or gaps therebetween.In any case, the tapered section 112 b″ and the beveled surfaces 124 b″may facilitate assembly and/or operation of the first bearing assembly100 b and an opposing bearing assembly, such as a second bearingassembly described herein.

Furthermore, the tapered section of the first bearing assembly may haveother suitable configurations, which may facilitate assembly andoperation of the first bearing assembly and another bearing assembly.For example, FIG. 3 illustrates a first bearing assembly 100 c, whichhas a support structure 110 c that include a bullet-nosed section 112c″. Except as otherwise described herein, the first bearing assembly 100c and its respective materials, elements, or components may be similarto or the same as any of the first bearing assemblies 100, 100 a, 100 b(FIGS. 1A-1C, 2) and their respective materials, elements, andcomponents.

In some embodiments, the bullet-nosed section 112 c″ may extendapproximately from superhard bearing elements 120 c″ and toward the endof the support structure 110 c. More specifically, in at least oneexample, the bullet-nosed section 112 c″ may start near beveled surfaces124 c″ of the superhard bearing elements 120 c″. Moreover, a portion ofthe bullet-nosed section 112 c″ may be configured in a manner that animaginary extension from the beveled surfaces 124 c″ is tangent to thebullet-nosed section 112 c″ along the length thereof. In any event, thebullet-nosed section 112 c″ and/or the beveled surfaces 124 c″ mayfacilitate assembly and/or operation of the first bearing assembly 100 cand another bearing assembly, such as a second bearing assembly, asdescribed herein.

Also, as illustrated in FIG. 4, an embodiment may include a firstbearing assembly 200 that has a support structure 210 and a plurality ofsuperhard bearing elements 220 (e.g., superhard bearing elements 220a-220 c) positioned about and an axis of rotation, such as an axis 10 a.Except as otherwise described herein, the first bearing assembly 200 andits respective materials, elements, or components may be similar to orthe same as any of the first bearing assemblies 100, 100 a, 100 b, 100 c(FIGS. 1A-1C, 2, 3) and their respective materials, elements, andcomponents. For example, the support structure 210 may include a bearingsection 211 and a tapered section 212 connected to or integrated withthe bearing section 211, which may be similar to the bearing section 111and tapered section 112 (FIGS. 1A-1D), respectively. In someembodiments, the first bearing assembly 200 may include one or moresuperhard bearing elements 220 located at and secured to the taperedsection 212 of the support structure 210.

In an embodiment, the superhard bearing elements 220 c may be secured toand/or within the tapered section 212 of the support structure 210. Forinstance, a beveled surface 224 c of the superhard bearing elements 220c may be substantially concentric with and aligned with an imaginaryextension of the tapered section 212. In one embodiment, the beveledsurface 224 c may be substantially concentric with but larger than outersurface of the tapered section 212. Optionally, the beveled surface 224c may define the tapered section of the first bearing assembly 200. Assuch, some embodiments may include the tapered section formed entirelyby the superhard bearing elements 220 c, and optionally solely by thebeveled surface 224 c thereof.

Furthermore, the superhard bearing elements 220 c may include a bearingsurface 221 c, which may be substantially parallel to and/or in planewith the bearing surfaces of the superhard bearing elements 220 a,superhard bearing elements 220 b. One example, area of the bearingsurface 221 c may be smaller than the area of beveled surface 224 c.That is, the surface area of the beveled surface 224 c may be smallerthan the surface area of the bearing surface 221 c. In addition, thelength of the beveled surface 224 c may be greater than the length ofthe bearing surface 221 c, as measured along a longitudinal direction ofthe bearing surface 221 c (i.e., along the direction corresponding tothe angle of the tapered section 212). Moreover, the bearing surface 221c may form an obtuse angle φ relative to beveled surface 224 c.

Also, in one embodiment, the superhard bearing elements 220 c mayinclude a thicker superhard table than the superhard bearing elements220 a and/or 220 b. In some embodiments, the thickness of the superhardtable of the superhard bearing element 220 c may vary depending on theangle of the tapered section 212 (e.g., to allow the bearing surface 221c to align with the bearing surfaces 221 a, 221 b, while maintaining thebeveled surface 224 c substantially aligned with the conical taperedsection 212 of the support structure 110). For instance, increasing theincluded angle of the tapered section 212 may require an increasedthickness of superhard table to allow the superhard bearing element 220c to have the bearing surface 221 c aligned with the bearing surface ofthe superhard bearing elements 220 a and/or 220 b.

Embodiments also may include hemispherical, semispherical, or generallydomed bearing elements mounted on the support structure of the bearingassembly. FIG. 5 illustrates a first bearing assembly 200 a thatincludes superhard bearing elements 220 a. Except as otherwise describedherein, the first bearing assembly 200 a and its respective materials,elements, or components may be similar to or the same as any of thefirst bearing assemblies 100, 100 a, 100 b, 100 c, 200 (FIGS. 1A-1C,2-4) and their respective materials, elements, and components. Forexample, the first bearing assembly 200 a may include a supportstructure 210 a that may be similar to or the same as the supportstructure 110 of the first bearing assembly 100 (FIGS. 1A-1B).

As noted above, the superhard bearing elements 220 a may have generallydomed bearing surfaces 221 a. Alternatively, examples of domed surfacesinclude semispherical, hemispherical, generally arcuate or nonplanarbearing surface or multiple bearing surfaces that may collectively formor define a dome. In any event, the superhard bearing elements 220 a maybe configured in a manner that facilitates assembly and/or operation ofthe first bearing assembly 100 c and another bearing assembly, such as asecond bearing assembly as described herein.

In some instances, the superhard bearing elements 220 a may be locatedon a tapered section 212 a of the support structure 220 a. Moreover, insome embodiments, the superhard bearing elements 220 a may include asuperhard table 225 a bonded to a substrate 226 a. For example, thesubstrate 226 a may be oriented at an approximately 90 degree anglerelative to a tangent line extending along the tapered section 212 a. Inother words, at least in one cross-section, the domed bearing surface221 a may be symmetrical relative to the line of the tapered section 212a (in that cross-section). It should be appreciated, however, that thedome-shaped superhard bearing elements 220 a may be positioned at anysuitable location on the support structure 210 a in a manner thatfacilitates assembly of the first bearing assembly 200 a and an opposingbearing assembly, such as the second bearing assembly.

In other embodiments, a concave radial bearing assembly with a taperedsection is contemplated. For example, a bearing assembly 300 isillustrated in FIG. 6. Except as otherwise described herein, the secondbearing assembly 300 and its materials, elements, or components may besimilar to or the same as any of the first bearing assemblies 100, 100a, 100 b, 100 c, 200, 200 a (FIGS. 1A-5) and their respective materialselements and components. For instance, the second bearing assembly 300may include a support structure 310 and a plurality of superhard bearingelements 320 secured to and/or within the support structure 310. Morespecifically, embodiments may include recesses 313 within the supportstructure 310, which may secure the superhard bearing elements 320therein. It should be appreciated, however, that the superhard bearingelements 320 may be attached to the support structure 310 in any numberof suitable ways, which may include securing the superhard bearingelements 320 to an inner surface 330 of the support structure 310.

Particularly, the second bearing assembly 300 may include an opening 331that may be, at least in part, defined by the inner surface 330.Furthermore, the superhard bearing elements 320 may have correspondingbearing surface 321 a-321 c which may rotatably engage the bearingsurfaces of the first bearing assembly, as described above.Specifically, each of the bearing surfaces 321 a-321 c may have aconcave shape that may correspond with the convex shape of the bearingsurfaces of the first bearing assembly, thereby allowing the secondbearing assembly 300 and the first bearing assembly to rotate relativeto each other. In some instances, the second bearing assembly 300 may bea stator, which may be secured to a nonmoving or nonrotating element orcomponent of a machine (e.g., a housing). Alternatively, the secondbearing assembly 300 may be a rotor. In any event, the second bearingassembly 300 and the first bearing assembly may rotate relative to eachother about an axis of rotation 10 b.

The second bearing assembly 300 also may include a tapered section 312.For example, each of the superhard bearing elements 320 c may include abeveled surface 324 c that may at least partially form or define thetapered section 312. Moreover, in an embodiment, the support structure310 may include a bearing section 311 and a tapered section 312. In oneembodiment, the tapered section 312 may generally have a shape of animaginary conical surface.

In some embodiments, the beveled surface 324 c may be approximatelyaligned with the tapered section 312. For instance, the beveled surface324 c may lie substantially on an imaginary extension of the surface ofthe tapered section 312. In some embodiments, the tapered section 312may include an axial gap between the beveled surface 324 c and thetapered section 312, while having the beveled surface 324 c and taperedsection 312 aligned with one another. Alternatively, the tapered section312 may have a substantially uninterrupted or continuous surface. Inother words, the beveled surface 324 c and the tapered section 312 mayhave no gap therebetween. In any event, the tapered section 312 mayfacilitate entry of another bearing assembly (whether it has a taperedsection or not) into the opening 331 in a manner that avoids or limitsdamaging the second bearing assembly 300 and/or another bearingassembly.

For instance, as the first bearing 100 is positioned within the opening331 of the second bearing assembly 300, the rotational axes 10 and 10 bthereof, respectively, may be misaligned relative to each other, asillustrated in FIG. 7A. It should be appreciated that, although thefollowing description refers to the first bearing assembly 100, any ofthe first bearing assemblies 100, 200 or other bearing assemblies may beassembled together with the second bearing assembly 300. As the firstbearing assembly 100 enters the opening 331 of the second bearingassembly 300, at least a portion of the tapered section 312 may contactat least a portion of the lead-in or tapered section 112, such that thefirst bearing assembly 100 may move or relocate toward the center axis10 b of the second bearing assembly 300.

In other words, the tapered section 112 and tapered section 312 mayfacilitate the first bearing assembly 100 and second bearing assembly300 to become centered relative to each other, such that the respectiveaxes 10 and 10 b thereof are substantially aligned with one another, asillustrated in FIG. 7B. Accordingly, the first bearing assembly 100 andthe second bearing assembly 300 may be assembled together to form abearing apparatus 400, without damaging the first bearing assembly 100and/or the second bearing assembly 300 as well as elements and orcomponents thereof. Furthermore, the tapered section 112 and taperedsection 312 may facilitate repeated disassembly and reassembly of thebearing apparatus 400 while reducing damaging or breaking the firstbearing assembly 100 and/or the second bearing assembly 300 or theirrespective elements and components.

As mentioned above, in some embodiments, the bearing surfaces of thefirst bearing assembly 100 may lie in or along an approximatelycylindrical imaginary surface. Such imaginary surface may have anysuitable diameter (i.e., the outside diameter of the first bearingassembly 100), which may vary from one embodiment to the next. In oneexample, such imaginary surface may have a diameter of approximate 4.0inches. One should appreciate, however, that the diameter of suchimaginary surface may be in one or more of the following ranges: betweenabout 1.0 inches and about 2.0 inches; between about 1.5 inches andabout 3.0 inches, between 2.8 inches and about 4.5 inches; and betweenabout 4.0 inches and about 8.0 inches. In other examples, the diameterof the imaginary surface may be greater than 8.0 inches or less than 1.0inches.

Similarly, as described above, the bearing surfaces of the secondbearing assembly 300 may lie on or along an imaginary surface that hasan approximately cylindrical shape (i.e., a shape approximating aninside of diameter of a tube). Such surface may have a diameter, whichdefines the inside diameter of the second bearing assembly 300, andwhich generally corresponds with the outside diameter of the firstbearing assembly 100. For instance, the bearing apparatus 400 mayinclude a clearance between the inside diameter of the second bearingassembly 300 and the outside diameter of the first bearing assembly 100that may facilitate relative rotation of the first and second bearingassemblies 100, 300. The clearance may vary from one embodiment to thenext and may depend, among other things, on the diameter of the firstand/or second bearing assembly 100, 300.

In an embodiment, the total clearance (i.e., the difference between theinside and outside diameters of the first and second bearing assemblies100, 300) may be approximately 0.5% to about 1% of the outside diameterof the first bearing assembly 100. For example, the first bearingassembly 100 may have an outside diameter of approximately 4.00 inches,while the inside diameter of the second bearing assembly 300 may beapproximately 4.02 inches, thereby forming a clearance of about 0.02inches between the first and second bearing assemblies 100, 300. In anyevent, the clearance between the first and second bearing assemblies100, 300 may be sufficient to facilitate assembly of the bearingapparatus 400 as well as relative rotation of the first and secondbearing assemblies 100, 300. Such a configuration may reduce binding ordamaging the bearing surfaces thereof during use.

Generally, rotational speeds of the first and/or second bearingassemblies 100, 300 may vary from one embodiment to the next. Forexample, the first bearing assembly 100 may rotate at approximately 20RPM to 100 RPM (e.g., about 20 RPM, about 30 RPM, or about 50 RPM),while the second bearing assembly 300 may be stationary relative to amachine component or element, as described below.

It should be appreciated that in some embodiments, the second bearingassembly may include beveled surfaces on bearing elements in other rows(i.e., in addition to the top row of the bearing elements. Similarly,the first bearing assembly may include beveled surfaces on the bearingelements located in rows other than the bottom or lowermost row. Forexample, FIG. 8 illustrates a bearing apparatus 400 a that includes afirst bearing assembly 200 a′ and a second bearing assembly 300 a′.Except as otherwise described herein, the first bearing assembly 200 a′and/or the second bearing assembly 300 a′ and their respectivematerials, elements, or components may be similar to or the same as anyof the first bearing assemblies 100, 100 a, 100 b, 100 c, 200, 200 a,300 (FIGS. 1A-7) and their respective materials, elements, andcomponents.

In at least one embodiment, all superhard bearing elements 220 b′ of thefirst bearing assembly 200 a′ may include beveled surfaces 224 b′.Likewise, all superhard bearing elements 320 a′ of the second bearingassembly 300 a may include beveled surfaces 324 a′. As such, beveledsurfaces 224 a′ and/or 324 a′ may facilitate entry of the first bearingassembly 200 a′ into the second bearing assembly 300 a′. Moreover, asthe first bearing assembly 200 a′ enters the second bearing assembly 300a′, the beveled surfaces 224 a′ and/or 324 a′ may reduce or eliminatechipping cracking of the superhard bearing elements 220 a′ and/or 320 a′that may otherwise occur if the superhard bearing elements 220 a′ and320 a′ contact one another at a sharp corner or edge.

It should be also appreciated that embodiments may include any suitablenumber of rows of bearing elements, some of which may include beveledsurfaces. Furthermore, one, some, or all of the bearing in such rows maybe superhard bearing elements, which may include diamond bearingsurfaces. Also, each row may include any suitable number of bearingelements (e.g., one, two, three, etc.), which may vary from oneembodiment to the next and may depend, among other things, on the sizeof the bearing assembly and bearing apparatus.

Embodiments also may include a second bearing assembly that has arelieved entry section to facilitate assembly and/or operation of thebearing apparatus. FIG. 9 illustrates a bearing apparatus 400 b thatinclude a first bearing assembly 200 b′ and a second bearing assembly300 b′. Except as otherwise described herein, the first bearing assembly200 b′ and/or the second bearing assembly 300 b′ and their respectivematerials, elements, or components may be similar to or the same as anyof the first bearing assemblies 100, 100 a, 100 b, 100 c, 200, 200 a,200 a′, 300, 300 a, 300 a′ (FIGS. 1A-8) and their respective materials,elements, and components. In particular, in at least one instance, thebearing assembly 300 b′ may include an entry region 310 b′ that may havean inside diameter that is 1% to 20% smaller (e.g., 5%, 10%, or 15%)than that outside diameter of the imaginary cylinder formed by thebearing surfaces of the superhard bearing elements of the first bearingassembly 200 b′.

In an embodiment, as illustrated in FIG. 10, the bearing apparatus 400may be incorporated into an agitator system 500. In an embodiment, thesecond bearing assembly 300 may be secured to a bottom of an agitatorcontainer 510. It should be appreciated that the container 510 may beconfigured to contain any suitable matter or medium, such as liquid,gas, and/or solid matter. Furthermore, in some embodiments, thecontainer 510 may be substantially leak-proof, such as to maintain thematter located therein without any significant leakage. Also, any of thefirst bearing assemblies 100, 200 may be secured to a shaft 520. In someinstances, one or more blades 530 also may be attached to the shaft 520or incorporated therewith. In addition, a motor 540 may be connected tothe shaft 520 and may rotate the shaft 520 together with the blades 530(e.g., inside the container 510). For instance, rotation of the blades530 may stir or agitate contents or medium located inside the container510. In some embodiments, the agitator system 500 also may include acover 550, which may at least partially enclose contents within thecontainer 510.

Hence, for instance, the first bearing assembly 100 may be inserted intothe second bearing assembly 300, in a manner described above. Sometimes,adding and/or removing contents to/from the container 510 may involveremoving the shaft 520 from the container and, thus, disassembling thebearing apparatus 400, by removing the first bearing assembly 100 fromthe second bearing assembly 300. Accordingly, the bearing apparatus 400may be disassembled and reassembled from time to time. As such, thetapered section of the first bearing assembly 100 and/or the secondbearing assembly 300 may facilitate damage-free disassembly andreassembly, thereby prolonging useful life of the first bearing assembly100 and second bearing assembly 300 as well as of the bearing apparatus400.

In some embodiments, the shaft 520 may be between 15 feet and 30 feetlong. Accordingly, a small angular displacement of the center axis ofthe shaft 520 relative to the center axis of the second bearing assembly300 may result in a substantial linear displacement. For example, a0.25° angular misalignment of the center axes of a 15 foot shaft 520 andthe second bearing assembly 300 may result in approximately 0.8 inchesof linear misalignment between the first and second bearing assemblies100, 300. Hence, the corresponding lead-in sections of the first andsecond bearing assemblies 100, 300 may facilitate alignment thereofduring assembly of the bearing apparatus 400. Moreover, in someexamples, a tapered section of the first and/or second bearingassemblies 100, 300 may facilitate a blind assembly of the bearingapparatus 400, during which the first and second bearing assemblies 100,300 may be invisible (e.g., obscured or hidden by the contents of thecontainer 500).

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments are contemplated. The various aspects andembodiments disclosed herein are for purposes of illustration and arenot intended to be limiting. Additionally, the words “including,”“having,” and variants thereof (e.g., “includes” and “has”) as usedherein, including the claims, shall be open ended and have the samemeaning as the word “comprising” and variants thereof (e.g., “comprise”and “comprises”).

We claim:
 1. A bearing assembly, comprising: a support structureincluding: a bearing section; and a tapered section connected to thebearing section; a plurality of first superhard bearing elements securedto the bearing section of the support structure, the plurality of firstsuperhard bearing elements being distributed about an axis to form aradial bearing surface, and each of the plurality of first superhardbearing elements having a superhard material including a first superhardbearing surface; and a plurality of second superhard bearing elementssecured to one or more of the bearing section or the tapered section ofthe support structure.
 2. The bearing assembly of claim 1, wherein thetapered section has a substantially conically shaped outer surface. 3.The bearing assembly of claim 1, wherein each of the plurality of secondbearing elements includes a beveled surface.
 4. The bearing assembly ofclaim 1, wherein each of the plurality of second bearing elementsincludes a second superhard material that forms a beveled surface. 5.The bearing assembly of claim 1, wherein each of the plurality of secondbearing elements includes a bearing surface having a second superhardmaterial.
 6. The bearing assembly of claim 2, wherein: each of theplurality of first superhard bearing elements includes a first superhardtable formed by the superhard material; and each of the plurality ofsecond superhard bearing elements includes a second superhard tableformed by a second superhard material, and the second superhard table isthicker than the first superhard table.
 7. The bearing assembly of claim3, wherein each of the plurality of second superhard bearing elementsincludes a substrate and a superhard table bonded to the substrate, andthe beveled surface passes through at least a portion of the superhardtable and through at least a portion of the substrate.
 8. The bearingassembly of claim 3, wherein the beveled surface of each of theplurality of second superhard bearing elements is substantially in planewith the tapered section of the support structure.
 9. The bearingassembly of claim 1, wherein the tapered section of the supportstructure does not include superhard bearing elements.
 10. The bearingassembly of claim 3, wherein the beveled surface of each of theplurality of second superhard bearing elements has a greater surfacearea than the radial bearing surface thereof.
 11. A bearing apparatus,comprising: a first bearing assembly including: a support structure; aplurality of first superhard bearing elements secured to the supportstructure and each having a first superhard bearing surface; and aplurality of second superhard bearing elements secured to the supportstructure, the plurality of second superhard bearing elements includinga beveled surface, the plurality of first superhard bearing elements andthe plurality of second superhard bearing elements at least partiallydefining an opening in the first bearing assembly, and the plurality ofsecond superhard bearing elements at least partially forming a firsttapered section of the first bearing assembly; and a second bearingassembly insertable into the first bearing assembly, the second bearingassembly including a plurality of third superhard bearing elements eachhaving a third superhard bearing surface sized and configured torotatably engage the first superhard bearing surfaces.
 12. The bearingapparatus of claim 11, wherein each of the plurality of first superhardbearing elements includes a beveled surface.
 13. The bearing apparatusof claim 12, wherein each beveled surface is oriented at approximately90 degrees relative to a leading side of each of the superhard bearingelements.
 14. The bearing apparatus of claim 11, wherein the secondbearing assembly includes a tapered portion.
 15. The bearing apparatusof claim 14, wherein the tapered portion of the second superhard bearingassembly includes at least some of the plurality of superhard bearingelements.
 16. The bearing apparatus of claim 11, wherein one or more ofthe first bearing surfaces of the first superhard bearing elements areconvex.
 17. The bearing apparatus of claim 16, wherein the first bearingassembly and the second bearing assembly form a radial bearingapparatus.
 18. The bearing apparatus of claim 17, wherein the superhardbearing elements of the first and second bearing assemblies are arrangedin multiple rows.
 19. An agitator system comprising: a container sizedand configured to contain a medium; a first bearing assembly secured toa bottom of the container, the first bearing assembly including aplurality of first superhard bearing elements each having a firstsuperhard bearing surface, and the first bearing surfaces defining anopening in the first bearing assembly; a shaft including one or moreblades attached thereto; and a second bearing assembly secured to theshaft and insertable into the first bearing assembly, the second bearingassembly including: a support structure including a tapered sectionsized and configured to substantially align a generally center axis ofthe second bearing assembly with a generally center of the first bearingassembly; and a plurality of second superhard bearing elements securedto the support structure and each having a second superhard bearingsurface configured to rotatably engage the first superhard bearingsurfaces.
 20. The agitator system of claim 19, wherein the taperedsection is at least partially formed by a plurality of third superhardbearing elements secured to the tapered section of the supportstructure.
 21. The agitator system of claim 20, wherein: each of theplurality of second superhard bearing elements includes a secondsuperhard table; and each of the plurality of third superhard bearingelements includes a third superhard table and the third superhard tableis thicker than the second superhard table.